Comparison of lineaments with bedrock structures along a cross-strike transect, eastern Massachusetts

Lineament data derived from three platforms, 1:58,000 color infrared photography (N = 770), 1:80,000 black and white photographs (N = 1106), and 1:250,000 SLAR imagery (N = 521), were used to determine the degree of coincidence between mapped faults and lineaments along a cross strike transect in eastern Massachusetts. The study area extends 27 km in an east-west direction and 8 km north-south and is located along the trace of a tunnel currently being constructed approximately 90 m below grade. Structural data are presently being collected from surface exposures along the tunnel trace and from within the 5 m diameter tunnel bore. These structural data will be compared with lineament data in the future. Reported here are the results of a comparison between the locations of lineaments and the position of major faults mapped on the Bedrock Geologic Map of Massachusetts (1:250,000). Lineaments were first mapped on acetate overlays in two independent trials and compared to determine which lineaments could be reproduced at the same geographic location. Reproducibility results indicate that 21 to 33% of the lineaments can be reproduced at the same spatial position and are comparable to results obtained from other studies. The length of reproducible lineaments proximal to and approximately parallel with mapped faults was compared with the total length of faults (137 km) within the study area. Results show that a small percentage of the faults are coincident with reproducible lineaments. Three percent of the lengths are mapped by reproducible lineaments observed on the SLAR imagery, 7% by the 1:80,000 scale photographs, and 5% by the 1:58,000 color infrared photography. This indicates that 97%, 93%, and 95% of the reproducible lineaments, respectively, are related to other geologic features in the bedrock or nothing at all.